The present invention relates to a plug for closing a hole, an opening, or the like of a container, a tube, or the like to prevent a fluid such as a liquid, for example, from leaking out of the hole, the opening, or the like, and more particularly to a medical plug of such a nature and an instrument equipped with such a plug.
Medical plugs for selectively closing and opening the holes, openings, or the like (hereinafter referred to also as a "hole") of containers, tubes, or the like for medical use, are primarily required to be of such a structure as to hold a fluid against leakage from the holes. These medical plugs are also required to be easily fittable into the holes of container, tubes, or the like for medical use, to be easily removable from the holes after they have been fitted, nevertheless to remain securely retained against accidental removal which would otherwise take place due to shocks, and also to be highly durable during long usage. Conventional medical plugs include:
(1) plugs which can entirely be force-fitted into corresponding holes, the plugs being made of a hard material for greater durability and tapered in the direction in which they can be pulled out; PA1 (2) plugs which can entirely be forced-fitted into corresponding holes, the plugs being made of a soft material for easy removal and higher shock resistance and tapered in the direction PA1 (3) plugs which can partly be force-fitted into corresponding holes, such as a sealing member or packing positioned on the front end of the plunger of a syringe and slidably fitted in the cylinder of the syringe.
The medical plug of the group (1), typically a syringe cylinder to be fitted into a hollow needle, is made of a hard material and can be force-fitted into the hole of a medical container, tube, etc. for liquid tightness. While the plug is highly durable, it is not easy to pull the plug out of the hole after it has been fitted in the hole. On the other hand, once the plug is positionally displaced even slightly by a shock applied, the plug tends to become loose in the hole due to the tapered configuration of the plug, with the result that the plug can easily be removed. In order to keep the plug liquid-tight against shocks, the plug has to be force-fitted into the hole more strongly. However, the strongly force-fitted plug cannot be pulled out easily when required. A plug made of a hard material may be designed for being partly force-fitted into a hole, but such a plug would be difficult to manufacture and highly costly.
The medical plug of the class (2), which may be a rubber cap to be fitted in a blood collector tube, is made of a soft material and achieves liquid tightness by being forcibly fitted in its entirety into the hole of a container, tube, or the like. The plug can thus easily be pulled out and is highly resistant to shocks. Since the plug is made of a soft material, however, it is poor in durability and can be deformed during sterilization, particularly autoclave sterilization. Therefore, the plug is normally forced-fitted into the hole under considerably strong forces. As a consequence, the plug cannot easily be fitted into and pulled out of the hole. The plug of the group (2) suffers from the same problem as the plug of the class (1) when it is subjected to shocks.
The medical plug of the kind (3) may typically be a packing to be fitted in the cylinder of a syringe. The plug (packing) of a soft material is partly force-fitted in the hole or space in the cylinder for liquid tightness. While this plug is highly durable, can easily be pulled out, and highly resistant to shocks, it will be fabricated by many manufacturing steps and hence is expensive.